1. Field of Invention
This invention relates to antennas adapted to receive transmissions from communication satellites which orbit the earth, and in particular to dish antennas.
2. Background Art
The antenna dish provides a relatively wide surface for capturing satellite radio frequency transmissions and is often shaped parabolically to focus parallel intercepted microwaves upon a pickup probe to provide an augmented signal to the antenna user. Such shaped dishes have commonly been formed of stamped sheet metal (e.g., aluminum or stainless steel), either as one piece units or, for larger antennas, of multiple parts that are assembled on site. Dish antennas have also been formed from a plurality of wedged-shaped antenna sections of metal mesh which are capable of reflecting the transmitted radio waves and which are supported in the dish shape by rigid radial ribs. The ribs are appropriately shaped such that the antenna sections are held in position to form a parabolic surface. Dish antennas formed of sections of metal mesh allow light to pass therethrough, and thus may be more aesthetically acceptable than a solid sheet metal antenna. The metal mesh also allows air to pass through, resulting in a lower wind load than would exist in a solid antenna of the same size. A particular advantage of mesh antennas over solid metal dishes is that the mesh antenna can be shipped in pieces in compact packages whereas the solid dishes are extremely large and bulky, requiring special handling procedures, and consequently are expensive to ship.
While the performance of mesh antennas is generally comparable to solid dish antennas, it has been found that the supportive rigid ribs, which are made of metal, are capable themselves of reflecting microwaves. The surface of the metal rib section at the joint where the rib engages the mesh is typically displaced from the surface of the mesh. As a consequence, the microwaves reflected from the metal ribs may be slightly out of phase with the microwaves reflected from the metal surface. Because the supporting ribs must be of high strength and resistant to corrosion when exposed to weather, the ribs have typically been constructed of expensive high strength aluminum or stainless steel.
It is desirable to connect the antenna mesh sections to the supportive ribs without unduly stressing the mesh sections. Connection has been accomplished by fitting the edges of the mesh sections into longitudinal grooves located along the metal ribs. However, the panels generally cannot be tightly fit into the grooves in the metal ribs, and connectors, such as screws, are required to hold the mesh to the ribs.